Esiris
Saew is right- it's worth discussing, and there are different kinds of being "closed", like being able to add people by unanimous vote.
Oh I agree it's worth discussing. And defining terms and how you use them is extremely important for the very reason that definitions aren't always set in stone, especially for the language of relationships.
I'm just explaining how I've always heard the term and my understanding of it. But then I used to hang around a very polarized poly-group as well with some people who absolutely abhorred swinging/open relationships and would be mortified if other people thought that polyamory=swinging/sexually open unless otherwise stated (as polyfi).
Plus I've personally been careful to differentiate between swinging and poly myself and find that to me at least they are very different animals. My relationship with Graverg started as only sexually open and it wasn't until years in that we added the romantic 'poly' side of things- so I personally have experienced them as separate entities and that's how I like to keep them.
And you're also right about there being different kinds of being "closed". Closed in the strictest sense that no one else is allowed in no matter what, closed in the sense that there need be unanimous decision to add another, closed in the sense that no one in the group is actively looking for new additions... There are at least a few options out there as well.